22 September 1846 – Taos county was established as one of seven original New Mexico counties under U.S. General Kearny‘s Code of Laws for the occupied Mexican territory.

9 January 1852 – All New Mexico counties were redefined. Taos county was extended west to the California border including land in present-day Arizona, and Nevada, and north into Colorado, a 500 mile stretch.

28 February 1861 – The northern part of Taos County, formerly New Mexico Territory, was transferred to the newly created Colorado Territory. All previous counties, including Taos County, were discontinued and new counties were created in the new Colorado Territory.

29 December 1863 – Arizona Territory was created from the western half of New Mexico territory. All previous counties, including Taos County, were discontinued and new counties were created in the new Arizona Territory.

18 January 1867 – Some of Arizona Territory’s land south of the 37th parallel and west of the Colorado River (previously including part of Taos County) was given to form the southern tip of the new state of Nevada.

Former Taos County land has been used to create parts of the following modern counties:

Where the genealogical records are. If an ancestor lived in what is now southeastern Colorado between 1846 and 1861 there is a chance he or she filed a land deed in Taos, New Mexico. Between 1846 and 1863 ancestors who lived in what is now northern Arizona or southern Nevada are not likely to have travelled to Taos, New Mexico to conduct their county business. Always check the present-day county for old deeds, but if you cannot find what you want, be prepared to search alternative counties like those discussed here.